Differential protection against SARS-CoV-2 reinfection pre- and post-Omicron.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly evolved over short timescales, leading to the emergence of more transmissible variants such as Alpha and Delta. The arrival of the Omicron variant marked a major shift, introducing numerous extra mutations in the spike gene compared with earlier variants. These evolutionary changes have raised concerns regarding their potential impact on immune evasion, disease severity and the effectiveness of vaccines and treatments.

BNT162b2 Versus mRNA-1273 Vaccines: Comparative Analysis of Long-Term Protection Against SARS-CoV-2 Infection and Severe COVID-19 in Qatar.

Background: This study provides a head-to-head comparison of the protection provided by the BNT162b2 and mRNA-1273 vaccines against SARS-CoV-2 infection and against severe COVID-19, covering primary series and third dose/booster vaccinations over up to 3 years of follow-up, both before and after the emergence of the omicron variant.

Methods: Two national, matched, retrospective cohort studies were conducted on Qatar's vaccinated population from December 16, 2020, to February 18, 2024. Subgroup analyses by pre-vaccination SARS-CoV-2 infection history, as well as sensitivity analyses, were also conducted.

Assessing the impact of annual health screenings in identifying noncommunicable disease risk factors within Qatar's primary health care corporation Qatari registered population.

Background: Noncommunicable diseases (NCDs) are a significant global health burden, including in Qatar, where cardiovascular diseases cause mortality. This study examines the outcomes of the annual health checkup implemented by the Primary Health Care Corporation (PHCC) in Qatar in detecting NCDs risk factors among Qataris aged 18+ years.

Methods: A cross-sectional study design was implemented to calculate the prevalence of behavioural and metabolic NCDs risk factors among Qataris who underwent annual health checkups between 2017 and 2019.

COVID-19 testing, incidence, and positivity trends among school age children during the academic years 2020-2022 in the State of Qatar: special focus on using CDC indicators for community transmission to evaluate school attendance policies and public health response.

Background: There exists a gap in our understanding of the age-dependent epidemiological dynamics of SARS-CoV-2 among school-age children in comparison to adults within the State of Qatar. Additionally, there has been limited assessment of the timely implementation of physical distancing interventions, notably national school closures, and their impact on infection trends.

Methods: We used the national database to capture all records of polymerase-chain-reaction (PCR) testing, and rapid antigen tests (RAT) conducted at all health care venues in Qatar and administered between August 26, 2020, and August 21, 2022, across all age groups (≥ 5 years old).

Post-COVID-19 syndrome, who at risk and why: an insight from Qatar 2022.

Background: Despite the recovery from the COVID-19 pandemic, many people experience post-COVID-19 syndrome, which negatively impacts their health and function. This condition has become a significant public health problem that requires immediate attention.

Objective: To study the prevalence, clinical characteristics, and predictors of post-COVID-19 Syndrome in Qatar during 2022.

Short-term side effects of BNT162b2 vaccine in primary care settings in Qatar: a retrospective study.

Background: Despite the established effectiveness of the BNT162b2 Vaccine, the novel technology demands careful safety monitoring. While global studies have explored its safety, local data remains limited and exhibits some variability. This study investigated short-term side effects among BNT162b2 vaccinated individuals in Qatar.

Effectiveness of two and three doses of COVID-19 mRNA vaccines against infection, symptoms, and severity in the pre-omicron era: A time-dependent gradient.

Background: Vaccines were developed and deployed to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This study aimed to characterize patterns in the protection provided by the BNT162b2 and mRNA-1273 mRNA vaccines against a spectrum of SARS-CoV-2 infection symptoms and severities.

Methods: A national, matched, test-negative, case-control study was conducted in Qatar between January 1 and December 18, 2021, utilizing a sample of 238,896 PCR-positive tests and 6,533,739 PCR-negative tests.

Protection of natural infection against reinfection with SARS-CoV-2 JN.1 variant.

Overall effectiveness of infection in preventing reinfection with SARS-CoV-2 JN.1 variant was estimated at 1.8% (95% CI: −9.

Addressing bias in the definition of SARS-CoV-2 reinfection: implications for underestimation.

Introduction: Reinfections are increasingly becoming a feature in the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, accurately defining reinfection poses methodological challenges. Conventionally, reinfection is defined as a positive test occurring at least 90 days after a previous infection diagnosis.

Tobacco control in Qatar from 2002 to 2022: 20 years of progress and challenges.

Tobacco use and exposure has been known as one of the leading causes of premature mortality worldwide. Tobacco control measures have been considered one of the strategies for reducing the burden of NCDs, improving public health, and strengthening the health system's response to threats and pandemics. The State of Qatar has put tobacco control a national public health priority as it has adopted various tobacco control measures that the WHO classified as high-impact measures.

Evaluation of warfarin management in primary health care centers in Qatar: A retrospective cross-sectional analysis of the national dataset.

Background: Warfarin management is associated with severe complications, highlighting the critical need to evaluate the quality of its administration.

Objectives: To evaluate the quality of warfarin management for patients managed in primary healthcare centers by measuring the percentage of Time in Therapeutic Range (TTR) and the proportion of extreme out-of-range international normalized ratio (INR) values.

Methods: This is a cross-sectional study.

SARS-CoV-2 infection and effects of age, sex, comorbidity, and vaccination among older individuals: A national cohort study.

Background: We investigated the contribution of age, coexisting medical conditions, sex, and vaccination to incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and of severe, critical, or fatal COVID-19 in older adults since pandemic onset.

Methods: A national retrospective cohort study was conducted in the population of Qatar aged ≥50 years between February 5, 2020 and June 15, 2023. Adjusted hazard ratios (AHRs) for infection and for severe coronavirus disease 2019 (COVID-19) outcomes were estimated through Cox regression models.

Turning point in COVID-19 severity and fatality during the pandemic: a national cohort study in Qatar.

Objective: To assess the evolution of COVID-19 severity and fatality in a unique setting that consistently applied, throughout the pandemic, rigorous and standardised criteria for defining severe COVID-19 outcomes.

Methods And Analysis: We conducted a national cohort study on 312 109 Qatari citizens to investigate incidence of severe, critical or fatal COVID-19 classified according to the WHO criteria between 28 February 2020 and 21 April 2023. Incidence rates for severe, critical or fatal COVID-19 were estimated during the pre-omicron phase, first omicron wave, combined phases and throughout the pandemic.

History of primary-series and booster vaccination and protection against Omicron reinfection.

Laboratory evidence suggests a possibility of immune imprinting for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We investigated the differences in the incidence of SARS-CoV-2 reinfection in a cohort of persons who had a primary Omicron infection, but different vaccination histories using matched, national, retrospective, cohort studies. Adjusted hazard ratio for reinfection incidence, factoring adjustment for differences in testing rate, was 0.

Short- and longer-term all-cause mortality among SARS-CoV-2- infected individuals and the pull-forward phenomenon in Qatar: a national cohort study.

Objectives: We assessed short-, medium-, and long-term all-cause mortality risks after a primary SARS-CoV-2 infection.

Methods: A national, matched, retrospective cohort study was conducted in Qatar to assess risk of all-cause mortality in the national SARS-CoV-2 primary infection cohort compared with the national infection-naïve cohort. Associations were estimated using Cox proportional-hazards regression models.

Seroprevalence of herpes simplex virus type 1 and type 2 among the migrant workers in Qatar.

Background: Limited data exists on herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) infections in migrant populations. This study investigated HSV-1 and HSV-2 seroprevalences and associations among craft and manual workers (CMWs) in Qatar who constitute 60% of Qatar's population.

Methods: A national population-based cross-sectional seroprevalence survey was conducted on the CMW population, all men, between July 26 and September 9, 2020.

Bivalent mRNA-1273.214 vaccine effectiveness against SARS-CoV-2 omicron XBB* infections.

Effectiveness of the 50-μg mRNA-1273.214 bivalent vaccine against SARS-CoV-2 infection was modest at 25% in a matched, retrospective, cohort study in Qatar comparing infection incidence in the bivalent cohort to that in the national no-recent-vaccination resident cohort. XBB* immune evasion, immune imprinting effects, or both, may explain findings.

Effects of previous infection, vaccination, and hybrid immunity against symptomatic Alpha, Beta, and Delta SARS-CoV-2 infections: an observational study.

Background: Protection against SARS-CoV-2 symptomatic infection and severe COVID-19 of previous infection, mRNA two-dose vaccination, mRNA three-dose vaccination, and hybrid immunity of previous infection and vaccination were investigated in Qatar for the Alpha, Beta, and Delta variants.

Methods: Six national, matched, test-negative, case-control studies were conducted between January 18 and December 18, 2021 on a sample of 239,120 PCR-positive tests and 6,103,365 PCR-negative tests.

Findings: Effectiveness of previous infection against Alpha, Beta, and Delta reinfection was 89.

The impact of COVID-19 on primary health care services in Qatar: 2 years of response and coping 2020-2021.

Background: Health care systems worldwide have rapidly responded to manage the COVID-19 pandemic by providing screening tests, contact tracing, treatment, and vaccination. However, the long duration of the pandemic has had an enormous load on the health care systems, which disrupted continuity of the essential non-covid services, long waiting time for appointments, and increase in the utilization of telemedicine services. Primary health care was established as an essential foundation for the global response to the COVID-19.

Sickness absenteeism among primary health care workers in Qatar before and during the COVID-19 pandemic.

Objectives: To explore the patterns, trends, nature, and extent of changes in sickness absence among health care workers (HCWs) at the Primary Health Care Corporation (PHCC) in Qatar-during the COVID-19 pandemic compared to previous years and uncover the main associated factors.

Methods: We conducted a retrospective analysis of all sick leaves' records of PHCC HCWs regardless of their profession from January 2019 till August 2021.

Results: A total of 41,132 sick leaves were taken during the studied period.

Long-term COVID-19 booster effectiveness by infection history and clinical vulnerability and immune imprinting: a retrospective population-based cohort study.

Background: Long-term effectiveness of COVID-19 mRNA boosters in populations with different previous infection histories and clinical vulnerability profiles is inadequately understood. We aimed to investigate the effectiveness of a booster (third dose) vaccination against SARS-CoV-2 infection and against severe, critical, or fatal COVID-19, relative to that of primary-series (two-dose) vaccination over a follow-up duration of 1 year.

Methods: This observational, matched, retrospective, cohort study was done on the population of Qatar in people with different immune histories and different clinical vulnerability to infection.